X-Pipe or Cat Bypass or 200 Cell Cat???

So I'm thinking of modding my exhaust and looking for a little info. I've looked on the inter-webs and can't seem to get the answer I'm looking for so I thought I'd try here. The options I'm looking at are X-pipe without CATs; CAT bypass/crossover (delete); or a 200 cell CAT to replace the OEM ones. So here are my questions... 1- Is there a sound difference between the three? 2- Do they impact performance? a) I've heard that X-pipes hurt low end torque but do they all do that or just the X-pipe? 3- Will they all cause CEL issues? a)If so, does adding the O2 sensor extenders fix that? Thanks for the help. BTW... this would be going on a 2003 C4S.

Hi friend, I just went thought this whole process trying to figure out what would be better between test pipe with O2 sensor relocation, 100 cells cats or 200 cells cats. Price for price the test pipe would be cheaper, you will lose low end torque but gain power in high rpm's but will trigger CEL so you have to adapt the O2 sensors pass the cats on this type of bung: http://www.bigdaddiesgarage.com/mini-cat-cel-fix.html I heard that the 100 cells cats will also trigger CEL code. So I opted for 200cells cats from Carnewal, no CEL, keep your bottom end torque and the soubd with my PSE exhaust is not bad at all They are using OEM cats and modify them with 200cells elements. http://www.carnewal.com/products/P96...nge-Sport-Cats My car is a C4S 02' all stock and want to keep it that way. After I heard about the Carnewal solution it was a no brainer for me.

Do you have emissions testing? if so go with a 200 cell x pipe, you won’t regret it if not go catless and retune I run a speedtech 200 cell x pipe on my 99c2 with afterhours cup mufflers, a little louder than some may like but it sounds great. Plus a few other mods too. i think it really did help how the car performs. plus how much are you really willing to spend. It’s not going to make a huge power increase but for sound it will.

Thanks for the responses! I'm leaning towards the 200 CAT just due to the idea that it seems easier and less likely to throw a code. My state will be ending the emission tax (I mean testing for a better environment) in 2020 and my car has just passed, so I'm free to go catless if I wanted to, but if it also means a loss of low end power and a retune, then I don't see the advantage (other than a few $$ saved). If others have ideas or a good source for acquiring the parts, I'm all ears. Cheers!

I've had 200 cell cats on both a 3.4 and a 3.6 996, both with aftermarket exhaust (Gemballa). Neither one threw codes, both performed better, they sounded better too, but I don't have any way to know whether that was a result of the exhaust, cats or the combination. Carnewal is a good source.

I just put on a 200 Cell X-pipe and honestly I didn’t notice much change. The torque seems the same, upper end seems to rev a bit better. Probably needs a retune to maximize the gains. However the exhaust note stayed quiet with the stock mufflers. I have since gundo modded them and it sounds a bit deeper, but still pretty tame. No CEL or any negative effects that I can point to either. Next step for me may be some more aggressive mufflers for some additional soundtrack. I wouldn’t hesitate to do the 200 Cell X-pipe.

i have went through a few iterations on my 3.4 stock cats + PSE is to quiet catless x pipe with pse exhaust sounds great but it seems to lose torque down low 200 cel x pipe and remove mufflers, sounds great and power is at least like stock or maybe a few hp, definitely 50+ pounds of weight reduction catless x pipe with no mufflers way to loud and loss of torque

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Does the 200 cel x pipe really attenuate the sound that much compared to catless? I would expect 200cel minus muffler would be pretty loud.

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Any muffler delete is going to be to loud.

what about dyno results? there are a lot of subjective reports so hard data from someone who isn't selling something would be good.

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That's what I figured, I've never done it. Although I do remember see a video where a guy did a bypass and I didn't think it was too crazy. Sometimes you can't really appreciate how it would sound IRL when watching a video, though. This is it. You Tube Definitely much louder, though.

Would be fun to try but I bet it would get tiresome as a daily driver.

Within the last 1.5 months I've had the FVD Brombacher/M&M catless x-pipe, NHP 200 cell crossovers, and now the TopGear 200 cell x-pipe in 54mm diameter on my 996.2. All with the same set of fister modded cans. The catless M&M x-pipe was by far the loudest and sounded absolutely glorious. It gives a completely different sound to crossovers, as is obvious in the videos of this pipe on youtube (I have an old review of this x-pipe on here somewhere). It's not too loud from inside of the car, but it's really loud to anyone outside. With the windows down at full throttle, you can hear it distinctly over wind noise well through 4th gear on an externally mounted gopro. Volume might be a concern on cold starts if you live in a neighborhood or if your local track has noise limits. Normal driving with windows up is quite civilized. No drone for me. My wife never noticed the pipe until I used lots of throttle in a tunnel. There's a dyno video on youtube from Ovalbore ( You Tube ) that shows he lost about 30hp below about 4k rpm and gained about the same above 4k with a fabspeed catless x-pipe. My butt dyno says that's about the same as what I felt with the M&M catless. really gutless between 3-4k, but made amazing power all the way through 7k. Sounds better than the Fabspeed to my ear. Powerband is really bad for slower autox, but really great for the track. 100% will give you a CEL. Had this on the car for a year/10k miles. Swapped back to my old NHP 200 Cell crossovers. Low RPM torque was back, car had a normal 3.6 powerband. I think the stock 3.6 has the kind of powerband that makes you want to short shift at 6k because it's pretty flat from there to 7k. The crossovers have a lower pitched sound so I think they penetrate into the cabin better. This setup was just as loud with the windows up in normal driving as the catless x-pipe. Catless is much louder and angrier at full throttle at high rpm and significantly louder from outside. I definitely missed the x-pipe sound and the high rpm power build of the x-pipe. (a few years ago I ran these NHP pipes every day for maybe 25k miles and never had a CEL) TopGear 54mm 200 Cell X-pipe has been installed for the last 3 weeks. This seems like the best compromise so far. From what I've read, larger pipes and no cats will slow exhaust velocity at low rpm. To prevent that and try and minimize low rpm losses, I chose the stock 54mm diameter pipes. The in/out of the exhaust cans is 54mm so I'm not sure what the benefit is to go wider, only to pinch back to 54mm at the mufflers. This pipe is MUCH quieter at low rpm with the windows up than either of the above. It was almost silent with windows up at super light throttle angles for the first 100 miles or so. Sounded nice with the windows down however. Tone is higher pitched like the catless x-pipe, but a little more civil and with less crackle off throttle. High rpm sounds great and is plenty loud, not quite catless loud, but at least as loud as the NHP crossovers. On the plus side, the sound is now a layer in addition to the orange cap mod instead of completely drowning it out like the catless did. It's getting a little louder as it breaks in too. Perfect volume inside, people outside say it's loud but not disruptively so. Power under 3k probably isn't quite as strong as the crossovers, but it's barely lower and doesn't effect drivability. By 3k it feels just as strong and continues to build linearly until 7k. You can still short shift and ride the substantial mid-range torque, but now the engine feels like it rewards you for revving it out to 7k. This change in character and willingness to rev-out is the best part IMHO. I did experience a CEL with the TopGear pipe, but that was while creeping along in DC at 25 mph for 25 min and barely touching the throttle. Reset it immediately with an OBDii scanner and it hasn't come back over a few hundred mile mix of freeway, city commuting, autox and track. Sorry I don't have any hard data from my own car, but having all of these on the car and autocrossing/trackcrossing on them all within such a short period of time was pretty eye opening.

Very cool info! Thanks

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I have the exhaust bypass (similar to the Fister mod) and it sounds great. It's a little louder than stock but no too loud. I daily drive mine on freeways and it doesn't "drone" at all.

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Good stuff, thanks for the review. I had seen that video the other day, he was claiming they gained 47whp on that car through the mods listed. That's seems a little out there. Most people seem to think 30 is the high end. I'm going to have to think about where I want to put my money once I get teh car. I sounds like Fister+200cel is a pretty good start. I'm considering CAI + X51 headers, as well.

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Yeah, the ability to make power with bolt-ons seems limited on these cars by all evidence (or lack thereof). Some things are worth it just for the sounds, so I think the calculus has to be weighted in that direction vs actually spending money for power. Seems like it's most likely that you'll just move power around from low to high rpm for a zero sum gain, but possibly a favorable tradeoff. I think +10hp is not improbable with 200 cells, but as people always point out, bolt-ons don't always work together. Headers start to get expensive and I haven't seen any dyno results on those so I'm hesitant considering the disaster the bolts are likely to be. Especially since the x-51 had cams, different heads, different intake runners and essentially a tune to make it all work. That's a LOT of stuff to get 25+ hp without compromising the delivery curve. The Ovalbore guys have another video where they dynoed the catless x-pipe with a tune and it didn't seem to change the delivery curve at all. A few years back I drove my stock car back to back with another 2003 that only had the Evoms intake. Sounded really nice, but no discernible difference in power according to my anecdotal butt dyno. There doesn't seem to be any evidence (aside from their manufacturers) that any of the intakes actually make power, but they can sound great so that's worth money in some instances. FWIW, when Im actually moving and the spoiler is in the up position, my obdii reader shows intake temps achieved by the stock box are within a couple degrees of ambient. That snorkel on the stock box must be pretty effective. I'm happy with how the car sounds now with fisters and the 200 cell 54mm x-pipe and I'm happy with the power delivery so I'm just calling it a day. If I really need more power, I think I'm better off selling the thing and finding one with the x-51 kit. Or just getting a GT3 :B

I went with the Top Gear 200 cell cats, but no x-pipe. I didn't want the mid rage drop in power. I like the sound. I would call it a little more bark. If it has produced any more power I haven't noticed. See: https://rennlist.com/forums/997-foru...o-results.html Stolen from that thread: Note slight drop in mid range, slightly more at top end. This is using a fabspeed x-pipe.

If I do anything I'll probably dyno before and after. I'm too analytical to do anything to my car without testing it.

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Hell yeah, can't wait to see the numbers! We need more of that and less opinions (which are all I have to offer haha)

The Dyno tests have all been done, visit Renntech and you'll see them.

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A lot of NA German cars seemed to be pretty tapped out from the factory. My Audi S4 with the V8, E46 M3 you had to pay a decent chunk of change to get some decent gains. Now the turbo cars are usually a tune and downpipe away from some serious gains but that seems to be most factory turbo cars. Anyway, one of the biggest benefits, especially if you go with a muffler bypass is the weight savings. Anytime you can remove 50-60 pounds from a car is pretty significant.

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Where would you find these on the RennTech site?

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Google the subject/topic

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I've done this a number of times over on renntech and I tend to find more people talking about how so and so had X Y or Z on a dyno and achieved ____ result, not actual dyno charts. I've found a number of places where some kind of dyno chart was posted so long ago that the image hosting service is now defunct and it's not visible. Maybe I also just suck at searching and can't find recent results. Either way, if Jkoravos wants to add to the knowledge base with his own fresh dyno data, it only adds to this community.

I have the car in the shop tomorrow for a PPI. They have a dyno on site, if the dealer says it's OK I'm going to have them do a baseline dyno. It's not my car yet, so they might balk at running it on the dyno.

I just noticed the shop that is doing the PPI has a 996.1 LS3 build on their "project car" page. I feel like I'm in good hands. https://kmcauto.com/project-cars/por...-gold-racecar/

I have a Cargraphic x-pipe with 200cel cats - it changed the way my car drives/feels but now i'm so used to it i'm not sure what its actually done. Previously I had TUV sound Cargraphic mufflers then added the x-pipe and it made the car quieter because the old cats were basically acting like a bypass. So I upgraded to Cargraphic super sound (non TUV) mufflers - now I love it. When I was talking to Cargraphic they did explain that crossover pipes can be louder but the x-pipe produces more power - just depends on what you're after. If you're going to do it - go with the x-pipe would be my recommendation. Plenty of brands but IMO Cargraphic and Fabspeed are the premium and both use HJS German cats which alone are quite expensive. Might as well change your O2 sensors while you're there too.

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Why change the O2 sensors? Prev maintenance or is there a different sensor that works better with the mods?

Good question - unfortunately no additional performance to be gained over stock just preventative maintenance. Just buy new Bosch ones - have heard others aren't as good and Bosch is the OEM

so going out on a devils ladder hear,, but,, Of all the things they could do to save money,, when they spend literally millions just on a air filter, I always wonder why folks think there is some magic left in the exhaust?/ Had a friend that worked at a local high end engine builder,, (Clients that can use anybody they want and race for a living... ) He dyno'd hundreds of Porsche's of all years,, and the way he summed it up is Porsche does the best job of making the power band wide, you can buy some top end, or some bottom end but nothing he ever tested had the fat power band the stock mufflers do. (ON a non modified engine)

More sound! Up to 11 haha

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One thing you do get is less weight. My gemballa mufflers weigh a fraction of what the stock cans weigh. The stock mufflers are incredibly heavy. And although I don't have any data, the mufflers and 200 cell cat setup feels quicker seat of the pants. It also sounds better. Please note the "feels" part of that- I tend to agree with your engine builder friend on an objective basis. Sometimes the feel and sound are enough to make it enjoyable though. Not because it gives you a power edge, but because it enhances the overall driving experience.

Butt dyno is REAL!!!

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Before changing the characteristics of your exhaust, consider how you want your car / engine to perform when you have completed your modifications. I would suggest not to go ***** nilly with changing this or that, only to next year find out you should have went with part B instead of part A. As OP have stated there are dyno charts out there, but like any kind of testing, the results can be skewed, not only the brand of dyno, but also something as simple as having the dyno warmed up or cold, can have an impact on the readings. There are so many choices for headers, cats and mufflers, the combination is endless. I can say if you go with an X pipe, consider a tune, you will lose torque in lower rpm range without a tune. Here is my dyno chart, this was run on a 70 degree day, cold dyno, it had not been run in 3 or 4 days. More than horsepower gains on top end, I was looking to achieve a very wide torque band, and achieve close to max torque well below redline. There is no reason to push a motor past it's optimal output, and if that can be done below redline, that will reduce any chance of pushing engine past it's structural limit. I went with a 63MM X pipe with 200 cell cats. But all of my engine mods were put together with focus on final results. BTW, I was not smart enough to do it. I had guidance. There are several good tuners out there, that can help. If it is just sound, that is just a matter of personal taste. Good luck David Here is what the dyno sounded like: https://www.youtube.com/watch?v=BtWGXExfGZE&t=13s

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Correct. Narrowing down your goals is the first step always. Evaluating results is another thing altogether. Dyno sheets are great, but only if you have a before/after that you feel are good comparisons. I was primarily looking for a different sound and possibly some compromise on low rpm power to get a little more at high rpm. How much of that compromise an individual is willing to accept is not something you can necessarily learn on a dyno. It all comes down to your use case and goals. What works great on a track car might be crap on a daily. I personally found it fun to play with different catalytic combinations and see what they were like to live with day to day and to track/autox. It's easy enough to sell any part you're not in love with on the classifieds and offset your spend, so for me it was not a lot of money spent on an enjoyable experience end to end. I don't think anyone should go into this thinking they're going to make a bunch of power. You're going to be tailoring how your car sounds to your personal taste and probably moving around how power is delivered. It can be a fun process if you're into that sort of thing.

I occasionally run 200-cell cats on my '99 Carrera 4. They're installed right now. I have seen a few emissions-related codes with the high-flow cats installed - but it's been infrequent enough (maybe three times over a year or two of runtime) that I haven't messed with extenders/anti-foulers/mini-cats. I like the noise the car makes (both the exhaust note and the additional backfiring/cracking @ shift points). Since I'm in CA and need to pass smog every two years, I got my muffler guy to torch the studs out of my factory cats and replaced them with new stainless hardware. As long as I remember to hit the O2 sensors with some penetrating oil ahead of time, the cat swaps only take about 30 minutes once the car is up on ramps... 1- Is there a sound difference between the three? I have run with cat delete pipes as well as 200-cell cats. I will never run catless again. The sound is obnoxious, and the exhaust smell can be much stronger. Catless did not meet wife's approval; 200-cell cats have not caused any wife approval issues. 3- Will they all cause CEL issues? No, but they CAN all cause CEL issues (meaning at least one guy in the Internet will have had issues with the part(s) you are interested in...). I was prepared to add mini-cats to mine, but I haven't needed to bother with them yet.

I personally don't agree with not running cats, cars aren't great for the environment - we don't need to make it any worse. 200CEL cats at a minimum get my vote.